I am unsure about the very last problem but I can help with the first two
1) (y+1)+4
If we combine the numbers 1 and 4, we get +5 and can isolate the numbers from the variable.
This would give us

2) (6*r)*7
remember that we do not have to explicitly state 6*r
Instead, we can write it as 6r
this helps us get rid of the parentheses
now we can write it as

I hope this helps!:)
So you you are trying to find the area of sphere so you would use this formula
A=4•3.14•r^2
And you already know that the radius is 6 so you would go ahead and plug in the numbers
A=4•3.14•4^2
4^2 is 16 so your final equation would be
A=4•3.14•16
And your answer is
=452.39
you will have 8 tables so
72 chair / 8 tables = 9 chair per table